Kanbanery Andoid App - Kanbanery on your Android device

Google Chrome browser extension - A browser extension that allows users to add new task cards to their board from the Chrome taskbar

PyKan - an open-source implementation of the Kanbanery API in Python.

Kanbanery iPhone App - a free application that allows view-only access to your Kanbanery boards. Later versions will allow full access to all board features.

kanbantastic - A gem wrapping the Kanbanery API

Ruby gem - Ruby client library and CLI for Kanbanery.com

Redmine_kanbanery - Simple redmine plugin that allows one to push issues over to kanbanery.com

Janbanery - The RESTful Kanbanery API Java connector

Janbanery-Shell - Kanbanery in your shell!

This one doesn't use the API, but it's kind of fun and might be useful to some: a bookmarklet to resize your Kanbanery columns

Kanbfire - Add comments to Campfire from inside Kanbanery

Kanbanery Feedback - is a set of tools for adding a modal feedback/bug report tool to your own Ruby, PHP, or Python app that creates a ticket in Kanbanery

Pivotal Tracker to Kanbanery importer - this doesn't use the API, but it's a useful script for parsing Pivotal Tracker's exported data to Kanbanery's csv import format